Control apparatus



Feb. 7, 1950 ELLloTT 2,496,453

CONTROL APPARATUS Filed Dec 16, 1945 9 Sheets-Sheet l IN V EN TOR.

Hard ail Feb 7, 1950 H. F. ELLIOTT 2,496,453

CONTROL APPARATUS Filed Deo.- 16, 1943 A 9 Sheets-Sheet 2 HE F! TE R5 A To cnrHoms INVENTOR.

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Patented Feb. 7, 1950 UNITED STATES PATENT OFFICE 23 Claims.

The present invention relates to control apparatus and more particularly to improvement in automatic tuning apparatus for radio receiving systems. This application is a continuation in part of Patent No. 2,411,617, issued November 26, 1947.

It is an object of the present invention to provide improved automatic tuning apparatus for a radio receiver, which is compact in arrangement, is of simple and inexpensive construction, and is positive and reliable in operation.

It is another object of the present invention to provide improved control apparatus in which a plurality of control units for selectively controlling the setting to which a settable element is moved, are selectively operated by individual driving motors arranged for selective energization.

According to another object of the invention, an electrical tuning system is provided in which each of a plurality of control units for driving a rotary control shaft in operative engagement with frequency changing means, is constructed to move the frequency changing means over its entire tuning range with a relatively low driving ratio, whereby the frequency changing means may be moved with precision accuracy to any desired setting.

In accordance with still another object of the invention, a pair of coacting lost-motion mechanisms are utilized in each control unit to provide the necessary connections for driving the settable element of the controlled device in either direction and for locking this element in a predetermined desired position to which it is moved, and the size of the unit in at least one dimension is minimized by arranging the lost-motion mechanisms of each control unit on parallel shafts which are common to the several control units.

According to a still further object of the invention, at least one of the lost-motion mechanisms of each control unit is comprised of a cam and cam follower assembly, thereby to provide for accurate positioning of the controlled device in an exact desired setting when the parts of the mechanism are lockingly engaged.

It is another object of the invention to provide a control unit of the character described, wherein improved facilities are utilized for releasably looking or clamping together two relatively movable parts of the unit in any desired positional relationship in order to change the setting to which the settable element of the controlled device is operated in response to actuation of the unit.

of the invention, elongated elements extending axially of a rotary control shaft common to the control units, and rotatable relative to this shaft, are utilized to releasably lock the relatively adjustable parts of each control unit in their desired relative positions.

In accordance with still another object of. the invention, all of the relatively adjustable parts of the several units, together with the facilities for releasably locking these parts in their relative adjusted positions, are mounted upon a third shaft which is separate from two parallel shafts upon which the lost-motion mechanisms are supported, thereby to provide a rugged structure and to facilitate adjustment of the relatively adjustable parts of any particular control unit.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which:

Fig. 1 is a fragmentar plan view illustrating improved control apparatus characterized by certain of the features of the present invention;

Fig. 2 is a side sectional view as seen along the lines 2-2 of Fig. 1;

Fig. 3 is a circuit diagram illustrating the manner of electrically energizing the driving motors individual to the control units of the apparatus shown in Figs. 1 and 2;

Fig. 4 is an end view taken along the lines 4-4 of Fig. 1, with parts thereof broken away to show the driving relationship between certain of the elements of one of the control units;

Fig. 5 is an end view as seen along the lines 55 of Fig. 1 illustrating certain parts of the control unit shown in Fig. 4 from the reverse side thereof;

Figs. 6, 7, 8 and 9 are fragmentary detail views of the lost-motion mechanism provided between two of the parts of the control unit shown in Figs. 4 and 5;

Fig. 10 is a fragmentary plan view illustrating a second embodiment of the invention;

Fig. 11 is an end view partially in section of the apparatus shown in Fig. 10 as seen from the right end thereof;

Fig. 12 is a view in sectional development, illustrating the details of the facilities provided in the apparatus of Fig. 10 for releasably locking each actuating element of the several control units in any desired rotary position relative to the shaft upon which these elements are According to a further and more specific object mounted;

' ii rig o;

shaft may be actuated through a driving connec tion provided by the parts of one of the control units;

parts embodied in the apparatus of Fig.

Fig. 1'7 is a side sectional view of certain of the Fig. 18 is a circuit diagram" iuiis'trating the manner of electrically energizing the electromag nets and driving motor of the apparatus shown Fig. 19 "isa detail the stack clamping "f ass'embly forming'a part of theapparatus shown :in Fig. 1;

-' Fig. 20 is an end view, partially in section, illustrating a m'odified arrangement for releasably 1 lockin the actuating or adjustable elements to the rotary control'shaft;

Fig. 21 "is a fragmentary side sectional view of the locking arrangementshown in Fig. '20;

"Fig. 22 is a view-in development of the locking arrangement shown in'Fig. 20;

Fig. 2 3 is an end new-illustratin a thirdfar- I rangement for I releasably locking the "actuating "or adjustable elements to the rotary control shaft;

Fig. 24 isa 'fraginentary side'sectional view of the locking arrangement shown in Fig. 23; and

Fig. 25 is a view' in development of the loci "ing arrangementshown in "Figs. 23 and 24.

Referring nowto the drawings, and more per.

" ticularl'yto Figs. "1 to 9, inchisive, and 19 thereof, it is pointed out that the "embodiment of the invention therej illustrated is also disclosed in "th above-identified cope'n'ding application. Accordingly. reference characters of like numerical "value haveb'ee'n utilized to identify like parts of the apparatus as disclosed in tooth applications.

JLBi efi d ie i i i g h fi leeie iapparatus there shown comprises frame means having 'e nd'plates I81 and I88 "which are rigidly held in spaced apart relatioi'i s'liip by means of tie rods (not shown) extendin therebetween and "rigidly secured thereto. As'sh'o'wn in Fig. 1, the

" apparatus is arranged to 'a'ctuat thesettable tuningshaft *I IIa of the tuning means III for a radio receiving system. through a pair of engaging gears II and I2, and in'cludesa'stationary or fixed shaft I86 which extends between the end plates I81 and I88 and is fixedly secured thereto by means of nuts 186a and 'I' 86b. A rotary control or drive shaft I89, whichcarrie's the'gear I I,'is "arranged parallel with 'the shaft 186 andisjrotatably supported in the end plates I81 and I88. Disposedbetween theend'plates I81 and I88 are a plurality of control units 13', "e'acli'of which is provided with its own'individual'drivin motor 26 and is operative to actuate the "settable element Ifla of the tuning means ID to a particular setting. comprises its own shaded pole'sin'gle phase alterinating current motor'26, having a rotor26a which 'is slip-clutch'connectedwith adrivin'g gear I91, "and a pair of lost-motion mechanisms"I4 and I5 respectively carried by the shafts I86 and I89.

Briefly considered, each control unit I3 I of which'isalso in meshing engagement with the motor driving gear I91 an'd the second of which is in meshing engagement with the gear I92 of the mechanism I4. The two gears of each of the two mechanisms I4 and I5 are respectively arranged "to be connected for relative and concurrent movement through spiral cam and cam follower assemblies ofthenovel character described below.

*As'bestsho'wn in Fig. 2 of the drawings, the slip clutch assembly through which the driving gear I91 of each control unit is connected to be driven bythe rotor 2521 of the associated motor 25, comprises'a sleeve ZBb Which'is rigidly secured to the rotor 26a"and serves rotatably 'to support this rotor upon the shaft 198. This sleeve is provided with a portion which extends axially "outw ardfrom'one side 'of ther'o't'or 26a to rotatably support the driving gear I91. One face surface of this gear is bias'edinto frictional engage- V ment with the end surface -'of the rotor 26a by means of a spring washer 26c, whichis d e forinied into a biasing position between 'th'e opposite side surface of the gear 'I91'and'thespun over end portion of theslee ve 25Gb. With"this arrangement,

the frictional engagemnt'between the side surfaces of thedrivinggear [91; the end surface of the rotor 26a and th'eprip'heraledge of the washer28c cause's'thegear I91 to be'r'otated'with the rotor 26a untilsuch time as thisgeai is locked against rotation through the 'oth'er'parts of the associated control unit in the manner explained below. A

As best shown :in' Fig. 1" of 'the drawings, the

gears I9I I92'o'f each control unit I3 are 'freely'rotatable dnthestationary shaft I86. Each adjaicent pair of gears I9l and I92 is separated by spacers [94,"while the "gears I91 and I92 provided i'n' each lost-'I'notion "mechanism I 4 are separated by spacers I96. The spacers Island I96 are also freely rotatable on'the shaft I86 so as not tdint'erferein anyway with the free rotation of the gears I9I an'd'I92. As indicated above,

each gear I9I is in meshing engagement with; a motor driving gear I91. -Each driving gear I91 ,is also in engagement with a gear 21H which is freely rotatable'on a's'le've or 'b ushing 292 "mounted on and splinedtothe'rotar ydrive shaft I89. Eachadjustableelment'or gear 203 is norcontinuous 'eiigagem'entwit'h the associated gear I92 carried by tl' eshaft I86. Each spacer or bushing member "202 'is formed with a shoulder portion 286 and a'reduced section for carrying the gear 28L A 'spacef'zoi -is mounted on the reduc'ed section of the bushing- 202 between the gear ZOLa'ndtheadjustable element 203. Also,

the gear 29I and element 203 of-each'control unit I3 are separated from'the next adjacent control .;unit spacers 2 0 9, the control-unit adjacent the end plates'T81 and"I88 being separated from these plates by collar or's'pacer members'209. Ad-

spacer member 208, as is clearly indicated in Fig. 1 of the drawings.

The frictional pressure serving to latch the adjustable elements 203 of the respective control units to the rotary shaft I 39 is controlled by the clamping unit 88 shown in Fig. 19 of the drawings, and the spring washer assembly 8386. More specifically, this assembly comprises a pair of wash-ers 83 and 84 separated by a spring washer 86 and disposed between the inner ends of the spacer member 200 and the adjacent end of the adjacent spacer member 208.

On separation of the Washers 83 and 84, force exerted by the dished spring washer 86 is released until the adjustable elements 203 of the control units l3 are permitted to rotate relative to the shaft 589 under but slight pressure from the spring washer 86, whereby these elements are rendered freely movable to adjusted positions in the manner more fully described below. When the washers 33 and 84 are clamped together, the spring washer 86 functions to press the spacer members 202 and 208 of each control unity together to engage opposite sides of the associated element 203, thereby to clamp this element in the As shown in Figs. 6 to 9, inclusive, each ad-' justable element 203 is formed with a corrugated face portion 2II to provide a spiral cam groove arranged for traversal by a lever or traversing arm 2I2. This arm is pivotally supported on the adjacent face of the gear 2M, and is formed with a pointed follower 2l5 which rides in the spiral corrugations of the gear 203. Thus, the spirally corrugated face portion of the gear or adjustable element 203 functions as a spiral cam and a the traversing arm 2 I 2 functions as a cam follower, the two named elements coacting to provide a lost-motion connection between the gear 20I and the gear or adjustable element 203. It is to be understood that the illustrated corrugated r structure as shown in Figs. 6 to 9, inclusive, is applicable to all of the adjustable elements 203 shown in Figs. 1 and 2 of the drawings. As shown in Fig. 4, each of the gears I92 is also formed with a corrugated face portion 2II' of spiral arrangement while each of the corre-' sponding gears I9I is provided with a pivotally supported traversing arm 2I2, the manner of engagement of the traversing arm with the spiral groove in the face of the gear I92 being exactly as shown in Figs. 6 to 9, inclusive, for the corresponding parts of the lost-motion mechanism I5. Thus, a spiral cam and cam follower assembly is utilized in each of the lost-motion mechain the face of the gear I92 radiates outward the gear 201 in one direction is limited by an inner abutment or stop' 2I3 while the limit vof the traversing arm travel in response to rotation of the gear 20I in the opposite direction is limited by an outer abutment or stop 2 I4, the abutments 2I3 and 2I4 being integrally formed in the adjustable element 203 in any desired manner. The travel ofv the traversing arm 2I2', as pivotally supported upon the gear I9I, is similarly limited by the stop or abutment members 2I3 and 2I4' which are integral with the gear I92 and are disposed at either end of the spiral grooveprovided in the face of this gear.

For the purpose of selectively controlling the energization of the motors 26 as provided in the control apparatus individual to the several control units, the control circuit illustrated in Fig. 3 of the drawings may be employed. Briefly considered, this circuit comprises a transformer from the axis of the shaft I86 in a direction control apparatus.

I34 having a primary winding I34a adapted to be connected to a suitable commercial frequency source of alternating current and a secondary winding I34b from which current for selectively energizing the motors 26 is delivered. The transformer I34 also includes a low voltage winding I340 for supplying cathode heating current to the heaters of the tubes provided'in the radio receiver equipped with the illustrated Two additional secondary windings I34d and I34e are provided which are included in the illustrated full wave rectifying circuit, this circuit being utilized to supply the screen'and anode potentials required by the various tubes provided in the receiver. In order selectively to control the energization of the motors 26, the cathode heating circuit, and the circuit over which +B voltages are delivered to the screen and anode electrodes of the tubes, switching equipment is provided which includes an off switch I36, push-button'switches I35 individual to the various motors 26, and a relay switching unit indicated generally at I26. This unit includes two mechanically interlocked magnets I21 and I28 having switch spring assemmeans of the receiver to the particular setting corresponding to the station which it is desired to receive. In order to initiate the operation of this control unit, the push button switch I35a associated therewith is actuated to its closed circuit position, thereby to complete a circuit for energizing the motor 26 individual to this control unit. This circuit includes the secondary winding I34b of the transformer I34 and the winding of the magnet I21. When energized in this circuit the magnet I2! attracts its associated latching armature I31, thereby to release the spring biased armature I3I of the magnet I28. The arm I3I in moving to its retracted position, closes the contacts I39a to complete the cathode heater circuit, and at the contacts I4I a and MN), completes the high voltage rectifying circuit in an obvious manner.

When the motor 26 of the selected control unit is energized, .the driving gear I9'I is driven portions 21 I and 2II"oflthe geais filliiand :I '92,

- respectively. The-gear I92 will remainstationary until coupling engagement thereof with the gear I9I is established through the :spiral cam and i cam follower by engagement of the fc'amzfollbwer 2 I2 with the inner'st'op'or abutment 3; or until a driving connection-to the gear I92 isestablished through the lost-motion mechanism *I5 "in? response'to engagement of the armor cam follower 2I2 with the outer :stop-or -abutment 2I4. Similarly, the adjustable-elementor gear 203 remains v in a stationary position until-the arm 2| 2 engages the stop 2I4 to-estab1isha :drivingeonnection through the gearS IS- 'I-and 20-I, or-until-the :arm

2I2' engages the stop 2 I3'-to establish a driving connection throughthegears I and 132. More .specifically, as the. gear I9I is rotated in a counterclockwise direction by the driving gear I91,

engagement withthe spiral groove formed=inthe I face of thegea'r I92,-is pivoted in a-counterclockwise direction so that the iollower end'thereof .is moved toward the sha'ft I86 or'toward a position for engagement'with 'thestop 2I3". "Similarly,-.

as the gear '20I is rotated'infa counterclockwise direction the cam follower 2I5 of the arm?! 2 follows thespiral cam formed in'thesu'rfa'ce of f the adjustable element 203 so "that the free end thereof is pivoted outward "toward thestop "or "abutment 2 I4.

Assuming that theparts thep'perating' control unit -I3 are initially so positioned relativeto each other that during the operation 'of this unit the arm 212 is moved-toengagethestop 2-I'4 befor the arm'2 I2 engages the stop 2I3',-'a driving "connection is establishedfor-rotating the adjustable element 203 'in a counterclockwise direction, this driving connection 'includingthe engaged -gears I 91 and I 'the'ar'm fl 2 and the stop' 21 4.

As the adjustable element 203 is rotated through this driving connection, the shaft I89 upon which the element 2I13is rigidlymounted is also rotated in a counterclockwise direction "to drive -the'isettable elem'entlfla of the tuningmeans Ill'toward :the desiredpredetermin'ed position. Incident t'o ,the rotation of the 'shaft I 89,-the gear I92,-which -meshes=with thegear or adjustable elementa2li3,

is'rotated in a clockwise direction about the shaft I88, thereby to increase the speed of relative movement between the gear I-92and-the gear I9 I Thus the speed with which thearrn -2 I 2 is moved toward the stop $213 is substantiallyincreased. Also incident to"therotation oftheshaft I89, the

adjustable elements 203 respectively provided-in the settable element Illa andthe'm'otor driving gear I 91. This locking connection 'is'establish'e'd by virtue of the engagement-of the-twotraversing arms 2I2 and 2I 2"with theirrespectiveas'sociated stops 2M and 21 3, "the toothed "engage- "m'ent between the three gears I 9 I fl91ai'1d'20 ha d the toothed engagement between "the gear I92 and the adjustable element or gear 203. Thus, operation of the settable element Illa is arrested when this element is moved to the predetermined position to which the control unit corresponds. After thelocking connection through the parts of this "unit is established, the rotor 26a of the energized motor 26 continues to rotate, relative movement between this rotor and the driving gear I9'I'being permitted through the slip clutch connection provided between these parts by the spring washer 260. In this regard it will be understood that "when the "settable element Illa of the tuning means I0 is operated to the position corresponding to the operating control unit, the particular desired station istuned in for reception to inform the operator that the tuning operation has been completed. Accordingly, the operator may release the push button switch Ia to deenergize thedriving motor of the control unit which is utilized to perform the desired tuning operation. Incident to the release of this push button, the

' winding of the magnet I 21 is also deenergized permitting the spring biased armature I31 of this magnet to move toward its locking position.

Assuming now that the parts of the particular control unit selected for operation are initially so positioned relative to each other that during oper- 'ation of the control unit the arm 2I2 is moved to engage the stop 2I3 before the arm'2I2 is wise "direction toward the predetermined posi- "tion corresponding to the operating control unit.

As a result, the speedof relative movement between the arm 2 I 2 and'the cam groove which the follower portion 2I'5 of this arm engagesyissubstanti'ally increased. Hereagain, when the arm 2'I2 -'is'moved to a position for "engagement with "the stop'2l4, a locking connection isestablished through the engaged parts of the controlunit 't'oarr'est the operation of the rotarycontrolshaft 189 and-the adjustable element 203. During the described reverse or "clockwise movement of the adjustable element 253- and the rotary control Ii'shaft I89, the movable parts of the nonactive =control unitss'are also moved to produce unl'ock Sing relativeimovement between the cam and cam follower parts of tone of the lost-motion mecha- -:nisms provided'in :each control unit, This fact will be more fully apparent from the following explanation :relating to the zmovement of .the -partsprovided in the control unit'shown in Fig. 4' of :the drawings when the rotary control :shaft 'I.B9- is driven by another of the .control units.

Assuming now that the rotary control shaft J89 has been operated to the setting correspondingito the control unit shown in Fig. l of the drawings, such that the arm 2 I2 engages the stop 2I4 and the arm I 2I2' engages the stop :2 I3, and that the .shaft I89is rotated by a :second control unit in a clockwise. direction, the .stop 2M remains in engagement with the arm 12 I 2 .to provide aldriving connection through :the -gear.2.0l andthe gear .I9Irfor'rotating'the gear I9! and the armIZIZ'ina clockwise direction laboutthe'shaft I86. Concurrently, the adjustable element'203in-its clockwise rotation drives the meshing gearil'92in a counterclockwise direction. With the two gears I9I and I92 rotating relative to eachother in the directions indicated,

the arm 2I2' is moved away from the stop 2I3',

and due to engagement of the cam follower 2I5' with the spiral cam provided in the face of the gear I92, the lower end of this arm is pivoted outward away from the stationary shaft I86. The described movement of the named parts of the control unit shown in Fig. 4 of the drawings, is of course arrested when the rotary control shaft I 89 is moved to the particular setting which corresponds to the operating control unit.

If, with the parts of the control unit shown in Fig. 4 of the drawings in looking engagement,

a third control unit is actuated to drive the ro- I tary control shaft I89 in a counterclockwise direction, the adjustable element 203 is rotated withdrawn until the adjustable elements 203 are Thismotor now drives the movable parts of the in a like direction. Due to the toothed engage-- ment between the element 203 and the gear I92, the latter element is of course rotated in a clock wise direction to drive the gear I9I in the same.

direction through the connection provided by the engaged stop 2I3 and arm 2I2. With the gear I9I rotating in a clockwise direction, the gear I is of course rotated in a corresponding direction. The relative movement thus produced between the gear 20I and the adjustable element 203 causes the arm 2I2 to be backed away from the stop 2M and to be pivoted inward toward the shaft I89 in a manner which will be clearly apparent from the above explanation.

From the above explanation it will be clearly apparent that the rotary control shaft I89 and the settable element IIJa actuated thereby may be moved to any desired setting through operation of a particular control unit Without any interference whatever from the nonactive control units. This is due to the fact that during operation of any one of the control units to establish the desired setting for the shaft I89, the parts of at least one of the lost-motion mechanisms provided in each of the nonactive control units are selected control unit until these parts are lookingly engaged in the manner explained above. Thus the adjustable element 263 of the operated control unit is actuated to a position relative to the rotary control shaft I89 such that when the two named elements are subsequently locked together, the control unit can thereafter only operate the rotary control shaft to the particular setting which it occupies when the locking operation is completed. The above-described procedure may be repeated for each of the other conmembers 208 is sufficient to maintain their relative positions upon the shaft I89. It will be understood in this regard that the spring washer 86 maintains all parts on the shaft I89 always under sufficient pressure for this purpose. When all of the control units I3 have been adjusted, J

. the screw 81 may be tightened to frictionally lock so moved relative to each other as to back the cam follower of the mechanism away from its associated stop. Thus, the two lost-motion mechanisms as provided in each control unit and as respectively mounted upon the two parallel shafts I86 and I89, permit the rotary control shaft I89 to be freely, accurately'and positively driven in either direction to any one of the predetermined settings respectively corresponding to the sev eral control units.

If at any time it is desired to turn off the re ceiver after a period of operation, the off switch I36 may be momentarily operated to itsclosed rides over the latching portion of the armature I37. After the switch I36 is released to deenergize the winding of the magnet I28, therefore, the armature I3I is held in its attracted position by the latching armature I3'I' of the magnet I21.

In order individually to adjust the adjustable elements 203 of the various control units relative to the rotary control shaft I86, thereby to provide for operation of this shaft to the desired predetermined settings by the various control units, the screw 8'! in the clamping mechanism 88 is all of the adjustable elements 203 in fixed positions relative to the shaft I89.

In the modified arrangement illustrated in Figs. 10 to 16, inclusive, of the drawings, the tuning means l0 of a radio receiver is adapted to be actuated to any one of a plurality of different settings, respectively corresponding to different stations, by a single driving motor 221. This motor is arranged to rotate the settable shaft Illa of the tuning means I0 through any one of a plurality of driving connections which commonly include the illustrated gears 228, 229, II and I2, and individually include the control units I3a, I317, 130, I311, I3e, I31, I39, I3h and I370. These control units are arranged to be selectively clutched to the drive shaft 230 upon which the gear 229 is mounted by means of nine electromagnetic clutching units individually associated therewith.

More specifically considered and as best shown in Fig. 10 of the drawings, all parts of the control apparatus are supported between or upon two spaced-apart parallel extending frame members 265 and 266. These members may have suitable tie rods extending therebetween and anchored thereto at the end portions thereof for the purpose of enhancing the rigidity of the structure.

The motor 227 is supported between the two plates bolts 28! are utilized to clamp the field structure 76 bi the motor 22'? in a position midway between the two frame members 265 and 266. This motor isprovidedwith a rotor shaft 'zfl-lcsuitably'jour mailedin the frame -members 265 and 266 and rigidly mounting the rotor 221a. The shaft 221c a dish shaped spring washer 221d, an assembly-- washer 22Ie and a spring retaining ring 221' More specifically, the rotor shaft 221b is provided at its projecting end with a portion of reduced diameter to provide a shoulder against which'the outer peripheral surface of the spring washer 221d may bear. The outer peripheral surface of thi's washe'r is in tensioned engagement with the adjacent side surface of the driving gear 228, the

Washer being maintained under tension by the retaining ring 221' which lies within a groove cut at the extreme outer end of the shaft 2210. This ring bears against the assembly or friction washer 221e which in turn engages the outer surface of the driving gear 228. It is noted in this regard that the driving gear 228 is freely rotatable relative to the shaft 2210 so that the only driving connection provided between the two named elements is that supplied by the described friction clutch assembly.

As best shown in Figs. 10 and 13 of the drawings, the nine identified control units are arranged between the two frame members 255 and 266 and each includes parts carried by three parallel extending shafts 24!, 242 and 256. The two shafts 24! and 242 are stationary and arefixedly supported by the members 265 and 266 at the-respective ends thereof. The third shaft 256 constitutes-the rotary control shaft and is journaled in the frame members 265 and 266 in the manner pointed out below. This shaft has 'thegear -"!I set screw mounted thereon at the end thereof which is adjacent the settable element !a'of the tuning means !0. The nine control units, which are axially disposed along the three shafts 24!, 242 and 255, areof identical constructionand arrangement. Accordingly, the arrangement of 'these units will be readily understood from a consideration of the control unit I370, the parts of which are detailed in' Figs- 10, Band 14 of the drawings.

In brief, this control unit comprises two lostmotion mechanism !4 and !5 respectively carried by the two shafts 24! and 242, and an adjustable element 255 which is in driven engagement with the two lost-motion mechanisms and is rotatable with the rotary control shaft 256; More specifically considered, the lost-motionmechanism' !4 comprises two gears 243 and 244 which are spaced'apart axially along the shaft 24! and are freely rotatable on this shaft for relative movement therebetween. establish a driving and locking connection between the two gears 243 and 244, a spiral cam andcam' follower assembly is provided therebetween which is of the exact character and construction'previously described with reference to 'Figs. 6 to 9, inclusive, of the drawings in the considerationofthe first embodiment of themvention. This assembly includes a traversing arm 245 pivotally supported upon the smaller ear 243'near the periphery thereof and provided with a cam follower 24'6-engaging a spiral cam groove formed in the opposite surface of the gear 244'. At the ends of this spiral groove, stop or abutme'n't elements 241 and 247a are provided, each of which is adapted to be engaged by the free end ofthe arm 245 to arrest relative movement between the two gears 243 and 244 an'd'thus pro-- In order to vide a direct connection between these gears. The 1 lost-motion 1 mechanism I 5 similarly comprises two'gears 249 and 250*which are spaced" apart axially alo'ng-theshaft 242 and are freely rotatable about this shaft for relative movement therebetween. A direct driveconnection may be established between the two enumerated gears through a spiral 'cam and camfollower assembly which comprises the traversing arm 25! pivotally supported upon the gear 249 adjacent the outer periphery thereof and provided with a cam follower 252 which engages a spiral groove formed in'the opposing face of the gear 250; At each end of this spiral cam groove, stop or abutment elements 253 and 253a are provided, each of which" is adapted to be engaged by the free-end of the traversing arm 25! gears 249 and '250, thereby toprovide a locking or driving: connection between these two gears. The two smaller gears 243'and 2490f the two lost-motion mechanisms are not engaged with each other, but are in continuous meshing engagement. with the adjustable element 255 carried by the rotary control shaft 256. The two larger gears 244 and 259 of the lost-motion mechanisms !4'and !5' are in continuous meshing engagement with each other and are arranged to be driven. from the drive shaft230 through the associated electromagnetic clutching unit 9. In'brief,'this unit comprises a pinion 236 mounted for rotation with the shaft 230 and arrangedin meshing engagement with an idler pinion 235,

pivotally supported by-means of a pivot pin 232 upon an L-shaped rocker arm 23! which is loosely mounted. upon' the shaft 236. Atits projecting end, the rocker. arm 231 carries an armature piece 231a'which. is adapted'to be attracted into engagement with the pole face of an electromagnet 238,.thereby to-move the pinion: 235'into meshing-engagement with thegear 244, in response to energization of the winding of this magnet.

Incthe interests of enhancing'the compactness of the structure, the clutchunits. 9, respectively associatedwith alternate ones of the control units: l3, alternately extend inward from the upper and lower edges of the two frame members.266 and265. Thus, the clutch unit 9 individual .to. the control unit-I31: is illustrated in Fig. 13 of the drawings as extendin downward from the upper edge of the frame'member 265, whereasthe clutchunit 9 individual to the next adjacent control unit I3h extendsupward from thelower'edge of the frame-member 265. The electromagnets 236 of the upper group of clutch units-13k, I39, I36, !3c and 3a are all bolted to a crossbar 239 which extends transversely betweenthetwo frame members 265 and 266 and is anchored to these members at the ends thereof. The electromagnets of the four lower clutch units I3h, I31; 3d and 3b are similarly bolted to a crossbar 240' which extends transversely between the two frame members 265 and 266 and is likewise suitably anchored to these frame membersat the ends thereof. With this arrangement, it 'isnecessary to drive the four control units I371, l3), !3d and 3b through the gears 250 individual thereto; Accordingly, the movable' parts 232', 235; 236' and 23! of the clutch units individual'to the four enumerated control unitsare carriedby a shaft 234 which is suitably journaledin the'frame members 265 and 266 and'is connected to be driven from the shaft 230- through a one to one driving connection 16 which comprises themeshing gears 23! and 233 after a predeterminedamount of relative movement between the two-- respectively mounted for rotation with the shafts 230 and 234. The idler pinions 235 of the clutch units individual to the four control units I 3h, I3f, l3d and 13b are thus arranged to be pivoted into meshing engagement with the gears 256 of the respective associated control units in response to energization of their associated electromagnets 238. In order normally to bias the rocker arm 23! of each clutch assembly to a position wherein the idler pinion 235 of the assembly is disengaged from the associated gear 244 or 250, each rocker arm is spring connected through a coil spring 2310 to a stop bar 2311) which extends transversely between the two frame members 265 and 266 and is anchored to these frame members at its ends. This bar is positioned to be engaged by the projecting end of each rocker arm 23'! and thus serves to limit the back stroke of each rocker arm when its associated electromagnet is deenergized.

The motor 227 is of the unidirectional type and may be so arranged that its rotor 221a and the driving gear 228 are rotated in a counterclockwise direction as viewed in Fig. 13 of the drawings. With the driving gear 228 rotating in this direction and as will be seen from Fig. 160., the idler pinions 235 carried by the upper shaft 236 are rotated in a counterclockwise direction, whereas the pinions 235 carried by the lower shaft 234 are rotated in a clockwise direction. Accordingly, when any selected idler pinion 235 is actuated into meshing engagement with its associated gear 244 or 250, the meshing engagement between the pinion and engaged gear produces a force which acts to pull the pinion into meshing engagement with the engaged gear,

thereby to lock the two elements in mesh during the tuning operation. Since this meshing engagement holds the armature piece 231a in its attracted position against the magnet pole face, a mechanical pressure urging the armature piece toward the pole face occurs concurrently with the electrical attraction of this piece by the pole face, whereby the magnet is aided in operating the movable parts of the clutch assembly. The magnets 238, therefore, need only be large enough to attract the armature piece into engagement with the pole faces of their respective associated magnets. This utilization of the mechanical reaction between any one of the pinions 235 and engaged one of the gears 244 and 250 pro vides for the use of relatively small magnets 238, since the magnet merely functions to initially engage the pinion with its associated gear; the pulling of the pinion into meshing engagement with the gear being sufficient to maintain the geared or interlocked engagement between the two elements so long as the pinion is rotating. The biasing springs 2310 individual to the several clutching units insure positive disengagement of the pinion 235 embodied in any actuated unit when the electromagnet of the unit is deenergized upon completion of a tuning operation. The described gear engagement may be further assured by providing a spring member 2300 which is anchored at one end 23011 to the shaft 236 by means of an anchor screw 2301), and at its opposite end 2362 is connected to the gear 228. The gear 228 is rotatable relative to the shaft 230, and the spring 2360 is arranged so that it is wound up when the motor 22'! is driving the shaft 232 through the gears 228 and 223. When the tuning means is operated to a selected setting in the manner explained below, the driving gear train is locked. Thereafter and when the motor 221 is deenergized, the spring 2300 backspins the rotor of the motor and thus assists in disengaging the operated clutch assembly.

The gears 243, 244, 249 and 25B are assembled upon their respective associated shafts 241 and 242 in the manner best illustrated in Fig. 17 of the As there shown, the gears 243 and upon the stationary shaft 242 is exactly similar to the mode of assembly of the gears 243 and 244 upon the shaft 24!. As previously pointed out, the adjustable ele ments 255 individual to the several control units are spaced axially along the third or rotary control shaft 256. Eachadjustable element 255 is in the form of a ring gear which is rotatably supported upon an annular locking ring 258 of slightly greater thickness than the ring gear. Along either side surface each locking ring 258 is engaged by an annular spacing ring 257 of slightly greater diameter than the outer peripheral diameter of the ring gear 255. Intermediate each adjacent pair of spacing rings 25'! an additional annular spacing member 259 is provided. In the assembly of the named parts carried by the shaft 256, these parts are arranged i in a stack between two end or assembly plates 26I. The parts of this stack are maintained in clamping engagement by means of three assembly screws 26-2 which are spaced angularly about the shaft 256, extend through registering openings formed in the parts 257, 258 and 259,

and are threaded into tapped drill holes provided in the end plate 26la.- As shown in Fig. 11 of the drawings, a driving fit between the inner periphery of the end plate 26m and the illustrated annular serrated surface 256a of the shaft 256 is utilized to lock the stack against movement relative to the shaft 256 so that a driving connection may be provided between any driven one of the control units and the gear ll. At the outer end of the serrated surface 256a, the shaft 256 is of reduced diameter, so that a shoulder is provided which cooperates with the inner end of the gear II to provide a bearing groove within which the adjacent bearing portion of the frame member 266 is disposed. The outer peripheral surface of the end plate 26! is journaled within an opening provided in the op- 1 gular position relative to the shaft 256 include a plurality of elongated camming elements 266, individual to the respective control units, which are radially disposed about the shaft 256 and extend in directions parallel to the axis of this shaft. These elongated camming elements each extend through registering openings provided in the end assembly plate 26], the spacing members 25l and 259, and the locking rings 258, and are each provided with an eccentrically cut camming portion 2600. which is adapted to coact with an integrally formed resilient portion 258a ofthe.associatedlockmg-ring258. More s'pecifia of each camming, elementwiththe parts of the.

structure through which,- it extends, the eccentric portion 269a acts, during rotation of the element to move the engaged clamping finger 2580. into and; out. of clamping engagement withthe associated adjustable element 255=along a path which extends radially-of theshaft-256. Dueto the inherent resiliency of. each locking finger 258a, this finger will follow the eccentric camming surface of the engaging camming element during. rotation of. this element. In order to facilitaterotation of the camming elements relativeto the other parts of the structure, each thereof is provided at its projecting end with a transverse slot for receiving the blade of a screwdriver or other suitable adjusting tool; As best shown by the developed illustration of the adjustable element assembly shown in Fig. 12 of the drawings, each camming element 26.0'only penetrates the structure of stacked elements 26l, 251, 258 and 259 to adepth required for engagement of its eccentric portion 262a with the clamping finger 258a, of the associated locking ring 258. Thusthe lowermost camming element 260 only penetrates the structure toa depth required for engagement of its eccentric portion 269a with the clamping finger 25812 of the locking ring upon which the adjustable-element 255 of the control unitv I3]: is rotatablysupported. The .next adjacent cammingelement 260 is of course'of slightly greater lengthand penetrates the structure to a depth permitting engagement of the eccentric portion 260a thereof with the locking ring 258 individual to the control'unit l3h. Thus, the camming elements individual to the various control units are of progressively increasing lengths. In the assembly of the camming elements with the. other parts of the stack structure, the cocentric portion of each camming element is interfitted with the slotted portion 2581) of its associated locking ring 258 before the two interfitted parts are assembled onto the other parts of the structure. This operation is necessary in order to permit each camming element to be rotated to a position where it may be aligned with the openings in the other parts through which it will extend when the assembly is completed. Thus, the stacking operation may best proceed by adding the parts to the structure in the orderof increasing length of the camming elements.

The resulting assembled structure is compact in.

arrangement, relatively light inweight, and pro-. vides for relative-adjustment of-anyv adjustable element relative to the shaft 253 and positive locking of any'adjustable element in any selected position to-which it ismoved.

As shown in Fig; 18 ofthe drawings, the control circuit for the embodiment of the invention illustrated in Figs. to-17, inclusive, is substantially similar to that provided for controlling the embodiment of they invention shown in'Figs. 1, 2

16 and 4 to 9, inclusive, of the drawings. The principal differences between the two circuits relate tothe substitution of the electromagnets 238 for the motors 26 and the series inclusion of the common driving motor 221 in the common portion of the circuits for energizing the respective electromagnets 238. Otherwise, the control circuit shown in Fig. 18 of the drawings is the same as that illustrated in Fig. 3 of the drawings.

In considering the operation of the control apparatus illustrated in Figs. 10 to 17, inclusive, of the drawings and described above, it may be assumed that the push button switch (35a corresponding to the control unit l3k is operated to its closed circuit position. In response to this operation, the electromagnet I21 functions to effectenergization of the rectifier circuit and the cathode heater circuit of the receiver in the exact manner previously explained. Also incident to closure of the switch I 35a, the winding of the electromagnet 238 individual to the control unit l3k is energized in series with the field windings of the driving motor 221. When the motor 221 is thus energized, the shaft 230 is rotated through a driving connection which includes the meshing gears 229 .and 228, and the slip clutch assembly which connects the gear 228 with the rotor shaft 2210 of the motor. As best shown in Fig 16a of the drawings, the shaft 230 -and the pinions 236 carried thereby are rotated in a clockwise direction through this driving connection. Due to engagement of the gear 23! with the gear 233, the shaft 234 and the pinions 236 carried thereby are rotated in a counterclockwise direction when operation of the motor- 221 is initiated. Thus, driving connections are established for rotating the idler pinions235 carried by the shaft 230 in a counterclockwise direction and for rotating the idler pinions 235 carried by the shaft 234 in a clockwise direction.

Incident to energization of the electromagnet 238 individual to the control unit ISk. the pole piece 231a of the clutch unit associated with this control unit is attracted, whereby the rocker arm 231 of the clutch.unit is pivoted about the shaft 230 to move the idler pinion 235 of the unit into engagement with its associated gear 244. Thus, a driving connection is established between the motor 221 and the relatively movable parts of the control unit l3k, Upon rotation of the gear 244, this gear and the meshing gear 250 are driven in opposite directions to provide for a traversal of the arms 24 5 and 25! over the spirally grooved portions of the two associated gears 244 and 250, respectively. The gear 243.will remain stationary until coupling engagement thereof with the gear 244 is established through the spiral cam and cam follower in response to engagement of the cam follower 245 with one of the two stop elements 241 and 24141., the particular stop element engaged depending upon the direction of radiation of the spiral cam groove from the axis of the shaft 24!. When the traversing arm or cam follower 245 is engaged by the stop 241, for example, a driving connection is established between the two gears 244 and 243. Similarly, the gear 249 remains stationary until the arm 25| engages one of the two stops 253 and 253a, or a driving connection for this gear is established through the adjustable element 255. Here again, the particular stop engaged again depends upon the direction of radiation of the spiral cam groove from the axis of the shaft 242. When the arm 25| engages the step 253,. for example, a looking or driving con- 17 nection is obviously established between the two. gears 250 and 249.

From the above explanation it will be understood that the mode of operation of the two lostmotion mechanisms l4 and I of the actuating control unit I3k is exactly the same as described above with reference to the embodiment of the invention illustrated in Figs. 1 to 9, inclusive. It will be understood, therefore, that during operation of this unit, a point is reached at which the adjustable element 255 and the rotary control shaft 256 are rotated in one direction or the other through one of the two lost-motion mechanisms I4 or I5. It will also be understood that when the rotatable control shaft 256 is rotated to the predetermined setting to which the control unit I3k corresponds, all parts of the control unit are locked against further relative movement through the engagement of the adjustable element 255 with the two gears 243 and 249 and the engagement of the traversing arms 245 and I with their respective associated stop elements 241 and 253. In fact, the entire driving connection extending back to the motor 221 is brought to a stop when the parts of the control unit I37c are locked up through the two lost-motion mechanisms I4 and I5. Thus, movement of the parts included in the driving connection between the motor 221 and the settable element Illa of the tuning means I 0 is arrested when the settable 1 element [0a is operated to the position corresponding to the control unit I3k. This will be more clearly apparent from a consideration of the parts as schematically illustrated in Figs. 16a and 16b of the drawings. nection is locked up in the manner just explained, relative movement between the rotor shaft 2270 of the motor 221 and the driving gear 228 is permitted through the slip clutch connection between these two parts. During the rotation of the rotary control shaft 256, the gears 243 and 249 of the nonactive control units I3a to I3h, inclusive, are obviously driven through the adjustable elements 255 of these nonactive units, and the resulting movement of the. parts within the nonactive control units causes the elements of at least one lost-motion mechanism in each nonactive unit to be disengaged in a manner which will be clearly apparent from the foregoing explanation.

When the new setting of the settable element Illa for the tuning means I0 is established in the manner just explained, the operator will be apprised of this fact through reception of the desired station and may release the push button switch 235a to deenergize the driving motor 221 and the energized electromagnet 238 in an obvious manner. When the named electromagnet is deenergized, its associated rocker arm 23'! is spring actuated by the associated spring 2310 to its normal position wherein the idler pinion 235 of the actuated clutching unit is disengaged from its associated gear 244. The manner in which the remaining control units may, throughselective energization of the magnets 238 by the push button switches I35, be actuated for the purpose of driving the settable element Illa to its other predetermined positions, will be clearly apparent from the above explanation with reference to the operation of the control unit [31s.

In order individually to adjust the adjustable elements 255 of the various control units relative to the rotary control shaft 256, thereby to provide for operation of this shaft to the particular settings desired, the camming elements 260 may be When the driving conand i 18 individually rotated to their unlocking settings to permit relative movement between their respective associated adjustable elements 255 and the rotary control shaft. Thus, when the shortest camming element 260' individual to the control unit I370 is rotated to a setting wherein the high point of the eccentric portion 260a thereof is disposed radially inward toward the shaft 256, the engaged clamping finger 258a of the associated locking ring 258 is disengaged from the inner peripheral surface of the adjustable element 255. After the locking connection between the shaft 256 and the adjustable element 255 is thus broken, the shaft 256 may be adjusted to a desired control position or setting by a suitable manual control knob (not shown) for the settable element Illa of the frequency changing means I0. While the shaft 256 is held in this position by manually gripping the control knob, the switch I35a associated with the control unit I3k is operated to energize the driving motor 221 and to engage the idler pinion 235 of the clutching unit individual to the control unit I370 with the gear 244 of this control unit. The motor 221 is thus rendered operative to drive the movable parts of the control unit I3lc until these parts are lockingly engaged in the manner explained above. Thus, the adjustable element 255 of the control unit I3lc is actuated to a position relative to the setting of the rotary control shaft 256, such that when the two named elements are subsequently locked together, the control unit can thereafter only operate the rotary control shaft to the particular setting which it occupies when the locking operation is completed. After the relative positions of the adjustable element 255 and the rotary control shaft 256 are thus established, the camming element 260 may be rotated until the eccentric portion 266a thereof produces a locking connection between its engaged clamping finger 258a and the inner periphery of the adjustable element 255. The above-described procedure may be repeated for each of the control units I3 in order to establish the other predetermined settings desired for the rotary control shaft 256, it being apparent that each camming element 260 requires individual actuation in order to release and then relock the associated adjustable element 255 relative to the control shaft 256.

Referring more particularly to Figs. 20, 21 and 22 of the drawings, modified facilities are there illustrated for releasably looking or clamping the adjustable elements 255 in the desired angular positions relative to the rotary control shaft 256. As there shown, each adjustable element or gear 255 is rigidly mounted upon the shouldered portion of a thin annular ring 280 which is slidable axially of and snugly embraces the outer peripheral surface of a sleeve 219. This sleeve is keyed or otherwise rigidly connected to the control shaft 256. Each element 255 may be spot welded or otherwise secured to the shouldered portion of its associated ring 280, the indicated rings, when arranged in their end-to-end relationship axially of the sleeve 219, serving to maintain the required spacing between the adjustable elements 255. At its right end as viewed in Fig. 21 of the drawings, the sleeve N9 is provided with an annular flange 219a which serves as an abutment against which the ring 236k may bear to establish the desired positions of the adjustable elements 255 axially along the shaft 256.

In order individually to lock the rings 289 against movement relative to the sleeve 275, each such element has associated therewith a cam locking assembly which comprises a cam element 282 disposed in a slot 28! cut transversely through a sector of the sleeve 219, and a cam actuating screw 283 which is threaded into the sleeve 218 and extends axially thereof. More specifically and as best shown in Figs. 20 and 22 of the drawings, the respective cam locking assemblies are disposed in different angular positions about the shaft 256 so that the screws 283 may occupy different and non-interfering angular positions Within the sleeve 219. In this regard, it will be understood that the slots 28! are spaced axially along the sleeve 2'19 so that each thereof is disposed directly beneath an associated one of the rings 28!). Each slot 28! may be in the form of a saw cut and terminates at an inner camming surface which is slanted relative to the shaft axis. in the manner shown in Fig. 21 of the drawings, so that the associated camming element 282 is faced radially outward when this element is moved axially of the shaft by the associated screw 283. Each screw is threaded into a tapped drill hole which extends axially of the sleeve 2'19 and bisects the associated cam receiving slot 282.

In considering the manner in which the screws 283 may be selectively actuated for the purpose of releasably locking their respective corresponding adjustable elements 255 relative to the control shaft 256, it may be assumed that with the rings 280 and adjustable elements assembled on the sleeve 279, the adjustable element 255 carried by the ring 28011, is to be rotated to a pre determined position relative to the shaft 258. To this end, the screw 283a is backed away from the camming element 282a a sufficient distance to permit this element. to be disengaged from the collar 289a. Following such disengagement of the elementsZSOa and 282a, the shaft 256 may be rotated to any desired position relative to the ring 280a without disturbing the settings of the other rings 280. After the desired setting for the ring 280a is thus established, the screw 283a may be driven inward to move the camming element 282a up the camming surface of the slot 281a, thereby to force the outer arcuate edge of this camming element against the inner peripheral surface of the ring. After engagement of the elements 280a and 282a is established and during continued driving of the screw 283a, the camming element 282a is tightly clamped between the inner surface of the ring 280a and the cam ming surface of the slot 28la. As a result, the ring 280a. and the adjustable element 255 carried thereby are tightly locked or clamped to the sleeve 219 in the desired angular position relative to the shaft 256. The other cam locking assemblies may be selectively actuated for the purpose of releasing and then relocking their respective associated rings 280 in new settings relative to the sleeve 219 and the shaft 256 in exactly the manner described above.

In the modified locking arrangement illustrated in Figs. 23, 24, and 25 of the drawings, each of the adjustable elements 255 is rotatably supported upon the shouldered portion of an associated annular ring 284. These rings are rigidly connected for rotation with the rotary control shaft 256. More specifically, the inner peripheral portion of each adjustable element 255 is seated upon a bearing surface 292 of reduced diameter which is formed b turning the associated ring 284 around the left edge of its outer periphery as viewed in Fig. 24 of the drawings. The axial width of the seat 292 thus formed is slightly less than the transverse thickness of the seated adjustable element 255. With this arrangement, the rings 284 not only serve to support the adjustable elements 255 for rotation relative to the shaft 258, but, in addition, serve to maintain the required axial spacing therebetween.

Clampin screws 29! disposed radially about the shaft 258 and extending axially thereof are utilized in cooperation with portions of the supporting and spacing rings 284 to releasably lock the adjustable elements 255 against rotation relative to the shaft 256. These screws are individual to the adjustable elements and extend different distances into the stacked ring assembly. More specifically, a sector of each ring is divided axially of'the shaft 256 into two parts 285 and 281 by splitting the ring radially inward from the outer periphery thereof to provide a slot 285. Centrally of this slot as provided in each ring, the portion 281 of the ring is drilled to provide an opening 288 for receiving the shank portion of a clamping screw 29!. In axial coincidence with this drill hole the portion 286 of each ring is counter-bored to provide an opening 289 for receiving the enlarged head portion of the screw 29 I. The threaded shank portion of each clamping screw is adapted to be threaded into a tapped opening 290 drilled into the last ring 284 which the particular screw penetrates. Thus and as best shown in Fig. 24. of the drawings, the shank portion of the clamping screw 29hr is threaded into a tapped 0pening290b provided in the ring 284b, which opening is axially aligned with the openings 288a and 289a of different diameters respectively provided through the portions 281a and 286a of the preceding ring 284a. When, therefore, the screw 29m is threaded into the opening 290?), the enlarged head portion thereof engages the portion 281a of the ring 284a to tightly clamp one sector of the associated adjustable element 255 between the ring portion 281a and the adjacent assembly ring 2841). This clampin operation may obviously be carried out without in any way altering the position of the ring portion 285a.

From the above explanation it will be understood that each ring 284 is provided with a number of openings therethrough around the face surface thereof. Thus the ring 284a not only includes the two openings 288a and 289a mentioned above, but is additionally provided with eight equiangularly spaced apart openings for accommodating the enlarged head portions of the eight other clamping screws. The second ring, i. e., the ring 284?) of the set is provided with the threaded opening 28Gb. At the next adjacent angularly displaced screw position this ring is also provided with the aligned openings 28% and 2881) through the portions 28Gb and 2811) thereof. At the other seven screw positions of the ring 284b, openings are provided for receiving the enlarged head portions of the clamping screws 29lc, 29ld, etc. The third assembly ring 2840 on the other hand, is only provided with openings at eight of the angularly displaced clamping screw positions therearound, i. e., a threaded opening 2880 for receiving the threaded shank of the clamping screw 2911), the openings 2880 and 2890 of different diameters intermediate the slot 2850 therein, and six openings for receivingthe enlarged head portions of the clamping screws 291d 29le, etc. The remaining sets of aligned openings in the ring 2840, which number six in all, are similarly arranged at the other six angularly displaced clamping screw positions about the shaft 256. It will thus be apparent that the clamping screws 28in,

29H), 2910, etc., are required to enter the ring stack for different distances and accordingly are of progressively increasing lengths. More specifically, the threaded shank portions of these screws are of the same length, only the enlarged head portions of the screws being of progressively increasing lengths.

From the above explanation it will be clearly apparent that by the simple expedient of unscrewing its associated clamping screw 29L any one of the adjustable elements 255 may be released for rotation relative to the shaft .256. It will also be apparent that when the desired relative positions of the shaft and the selected adjustable element are established, the associated clamping screw 29f may be tightened to positively clamp the adjustable element against rotation relative to the shaft 256. This selective adjustment of any desired one of the adjustable elements 255 is acomplished, moreover, without in any way releasing the clamping pressure which maintains each of the other adjustable elements in its set position relative to the shaft 256.

It will be understood from the preceding description that the elements of the assembly for adjustably supporting the adjustable elements 255 upon the shaft 256 are assembled upon the shaft in the order of decreasing length of the respective associated clamping screws. Thus the adjustable element 255 to be supported by the ring 28410 is first assembled upon the shouldered portion of this ring, following which the ring 28 th is telescoped over the end of the shaft into engagement with the inner peripheral portion of the assembled adjustable element 255. The ring 28% may now be rotated until the openings 288a and 239a thereof are brought into registry with the opening 29% of the ring 28470, following which the clamping screw .29l7c may be inserted through the openings 289k and 28871 and threaded into the opening 296k. The second adjustable element 255 may now be assembled upon the shouldered portion of the ring 2847i, after which the ring 284g may be telescoped over the shaft 256, with the screw 29 lk being received within the proper opening through the ring 2849 to insure alignment of the openings 2899 and 2889 with the opening 29% of the ring 28 th. After the ring 284g has thus been brought into engagement with the inner peripheral portion of the adjustable element carried by the ring 28 th, the clamping screw 29|h may be inserted through the aligned openings 2899 and 288g and threaded into the tapped opening .2 9671 of the ring 28471.. The manner in which the remaining elements of the assembly are added to the stack in progressive fashion will be clearly apparent.

From the preceding explanation, it will be clear that in each of the three disclosed arrangements for releasably locking the adjustable elements 255 gaainst rotation relative to the shaft 256, each element 255 may be released for adjustment without in any way disturbing or releasing the locking connection provided between each of the other elements and the shaft. Thus positive and accurate positioning of the elements 255 relative to the shaft 256 is insured. It will be noted further that the locking structures require only a small amount of space and a relatively small number of parts. Accordingly, any one of the three disclosed structures may be manufactured in production quantities at low cost. The operations required to assemble the parts of any one of the structures are, moreover, exceedingly simple and units and each supporting one of the lost-motion 22 may be performed with practically no possibility of error.

While different embodiments of the invention have been disclosed, it will be understood that various modifications may be made therein without departing from the scope of the invention as defined in the appended claims.

I claim:

1. In apparatus Which includes driving means for moving the tuning element of a radio receiver to a predetermined setting, a. control unit for arresting the movement of said tuning element when moved to said predetermined setting and comprising, in combination, a pair of parallel shafts, coacting lost-motion mechanisms respectively carried by said shafts, and means including said lost-motion mechanisms for arresting the movement of said tuning element when said tuning element is moved to said predetermined setting.

2. In apparatus which includes driving means for moving the tuning element of a radio receiver to a predetermined setting, a control unit connected between said driving means and said tuning element to actuate said tuning element in response to operation of said driving means and comprising, in combination, a pair of parallel shafts, lost-motion mechanisms respectively carried by said shafts and respectively operative to provide driving connections for moving said tuning element toward said predetermined setting from reverse directions, and means including said lost-motion mechanism for locking said tuning element against continued movement when said tuning element is moved to said predetermined setting from either direction.

3. In apparatus for variably setting a control device in any one of a plurality of different settings, a pair of parallel shafts, a plurality of control units disposed axially along said parallel shafts and each corresponding to one of said settings, each of said control units including two coacting lost-motion mechanisms respectively carried by said parallel shafts, and means including said control units for selectively operating said device to any one of its settings.

4. In apparatus which includes driving means for variably moving a control device to any one of a plurality of different settings, a pair of parallel shafts, a plurality of control units connected between said driving means and said control device and each operative to actuate said control device in response to operation of said driving means, each of said units including two lost-motion mechanisms respectively carried by said shafts and respectively operative to provide driving connections for moving said control device in different directions, and means including the lostmotion mechanisms of any operated one of said control units for locking said control device against continued movement when said control device is moved to the particular setting corresponding to the one unit.

5. In apparatus for variably moving a settable element to any one of a plurality of different settings, a plurality of control units each connected in driving relationship with said settable element and with each other and each corresponding to a different setting of said element, each of said control units including a pair of coacting lost-motion mechanisms for arresting the operation of said settable element when said element is operated to the corresponding one of its settings, a pair of parallel shafts common to said control 

